Friday, September 19, 2008

Migrating Bird's Strange Sixth Sense
I thought this was especially interesting since it relates to what we have been talking about in class. An article in the October 2008 issue of popular science, found here, discusses a new theory as to how a bird is able to navigate over long distances. Their navigational abilities are in part due to "magnetite" in the bird's beak, which let them detect the Earth's magnetic field. But their ability to detect direction may be in part to a newly discovered compound, called a CPF triad located in the retinas of migratory birds. When a bird's eyes are lit up with a level of light similar to that found at dusk, the compound forms "two unpaired electrons that spin in oppposite directions." The Earth's natural magnetic field forces those unpaired electrons to align north, giving the birds a sort of natural compass. The birds may be able to actually see the planet's magnetic field. Henrik Mouritsen of the University of Oldenburg in Germany compares this system to the head-up display of a fighter pilot

Posted by Corinne Delisle
Week one

Edit 9/23
To answer some of the questions and comments, I searched online for other versions of this article that give a little more information. When the bird's retina absorbs light, a chemical reaction is triggered that produces a substance which is sensitive to the magnitude and direction of the Earth's magnetic field. Apparently this is supported by experiments in which blue light photoreceptors have been found in the retinas of birds. "CPF" stands for "Carotenoid Porphyrin Fullerene". These are the molecules that are linked to form the triad. Each triad unit contains a pair of electrons with a neurtal pair of electrons in the ground state. When the molecule is exposed to light, a reaction occurs and the poryphyrin is promoted to an excited state. This starts a kind of chain reaction, the result of which is the CPF molecule existing in a charge seperated state. The unpaired (charged) electrons are then able to react to a weak magnetic field.
Picture Credit: Zina Deretsky, National Science Foundation

(This information came from this webpage.)

To answer the question about Hund's rule, all electrons in singly occupied orbitals have the same spin. For example, I think there are 5 3D orbitals. If there are five or less electrons among those orbitals, they will spread out and all will have the same spin. But I believe when a pair of electrons share an orbital, then they have opposite spins. For example, there is only one 4s orbital, so the electrons can't spread out. One electron in the orbital will have an "up" spin, and the second will have a "down" spin.


At 10:27 AM, Anonymous Anonymous said...

That was a very interesting summary, and i like how it fit nicely into topics of class. I was wondering if they had found this compound in nonmigratory birds, and maybe if the compound is found in different intensities depending on the birds and how far they migrate. i think this study is going to bring about many conversations in the future.

Amanda Joyce (21988031)

At 1:03 PM, Anonymous Anonymous said...

I am curious as to how this affects the vision overall. Does it make them able to see better or worse, or have no effect? Also, why would this form of vision only be active at dusk? On a side note you should mention what CPF stands for, but overall this was really interesting and a fun read.

Posted by: Alex Jackson

At 1:05 PM, Anonymous Anonymous said...

I really enjoyed your post. I was wondering if this "magnetite" is only found in migratory birds? Is it possible for regular stationary birds to have this as well? It would seem that any kind of bird would benefit from it. Do you know if the migratory birds always had this, or was it evolutionarily added? Great topic I think that the lifestyles of migratory birds are very interesting and deserve some more attention.

Mia DiFabbio

At 4:41 PM, Anonymous Anonymous said...

I found this to be an interesting article. It seems birds have many ways of navigating. If a certain light level triggers the CPF inthe retinas, what about during the day when there is bright sunlight? Is it inactive, partially active? If it is inactive do they use other means of navigation? Overall, I found it to be an excellent summary.

Duy Nguyen

At 1:24 PM, Blogger Brena said...

This is a very interesting article because it fits right into what we were talking about in class. But I just have a couple of questions about the article in general: How did this scientist discover this "CPF Triad" (not sure what CPF stands for)? How did he test this hypothesis that this compound forms "two unpaired electrons that spin in opposite directions"?
Besides missing a couple of details I think this was a great summary of the article!

Posted by: Brena Sena

At 1:30 PM, Anonymous Anonymous said...

Although I find this fact to be interesting and reasonable, there is still one thing that doesn't add up.
According to the consensus in modern chemistry, unpaired electrons always pair up in the same direction(with the same spin), this is known as Hund's rule. Therefore, having two electron pairs in opposite direction contradicts the basis of modern chemistry.

Noam Pelleg (21997016)

At 4:42 PM, Anonymous Anonymous said...

Any idea on how these scientists were able to find these free electrons and the experiments they used to come up with this finding?

Allan Eldridge

At 4:51 PM, Anonymous Anonymous said...

Animals with senses beyond ours always interest me. Do you know how they tested this? Why is the level of light important? And I'm a little confused, can the birds "see" the magnetic field in a literal sense?

-Jane de Verges

At 6:44 PM, Anonymous Anonymous said...

Very interesting article. The possibility of birds actually being able to see the magnetic field. Makes me wonder if any other animals have this ability?

Alex Pavidapha

At 7:23 PM, Blogger PWH said...

I wonder how it could be tested the amount CPF and magnetite factor into migration compared to other things.

Charles Scondras

At 9:36 PM, Anonymous Anonymous said...

Great article as it is very relevant to our current topic. My major question is, do birds have other ways to detect direction other than through this compound? Since I believe there must be other ways for them to do so as this compound only forms with a certain level of light. What happens for the rest of the day when the light is brighter?

Posted by Tazneena Ishaque

At 11:41 PM, Blogger PWH said...

That definitely expands the horizons to what senses birds use to navigate around the world. Not all birds travel just north to south so to have other senses helping them to their destination is definitely great possibilities.

-Posted By: Heather Scott

At 8:47 PM, Blogger PWH said...

Thats really interesting. In chemistry I learned about this unpaired electron phenomina and how it can be used with the magnetic field but I never would have guessed that creatures can have it in their eyes. This theory definitely has some scientific backing as well. If this is true, this links their sense of direction directly with their eyesight rather than the old theory that high levels of iron in their brain somehow enabled them to have direction. I wonder if the birds actually see the magnetic poles like fighter pilots or if its just a sense of them? I also wonder if this compounds works directly with the iron found in their brain and their ability to read the star formations at night?

Patrick Salome

At 10:30 PM, Blogger PWH said...

Great topic! I think you can write a bit more to clear up some of the partial confusion. What species of bird was this tested on or were the tests run on several species of migratory birds? Do non-migratory birds lack this "sixth sense" or do they have this sense as well to direct themselves from place to place. This is a very interesting topic; I would like to know more. Good work.

Carlos A. Varela


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